1. Field of the Invention
The present invention relates to a substrate holding apparatus which is applied to a substrate processing apparatus such as a semiconductor manufacturing apparatus (e.g., a rotation type substrate processing apparatus, a substrate transporting apparatus).
2. Description of the Prior Art
In a rotation type substrate processing apparatus (such as a rotation type coating apparatus and a rotation type developing apparatus) for processing a semiconductor wafer, a liquid crystal glass substrate and the like (hereinafter "substrate(s)"), while rotating a substrate, it is necessary to suppress slipping between the substrate and a member which holds the substrate as much as possible. As the substrate is chipped away at a surface if slipping occurs, not only the substrate is damaged but also dust is created, which in turn deteriorates the cleanness. Further, as processing liquid does not flow uniformly, the quality of processing of the substrate is degraded. Hence, the following technique which suppresses slipping of the substrate has been conventionally provided.
FIG. 18 shows a conventional substrate holding apparatus 900. A plurality of substrate holding members 902 which are disposed on a top surface of a rotation stage 901 are obtained by forming substrate holding parts 903 and horizontal position restricting parts 904 integral with each other. As a top surface of the substrate holding part 903 touches an outer peripheral portion of a bottom surface of a substrate W, the substrate W is held horizontally with a distance from the rotation stage 901. Side surfaces of the horizontal position restricting parts 904 touch an outer peripheral portion Wa of the substrate W and accordingly restrict the position of the substrate W on a horizontal plane. Further, a substrate pressing member 911, which is supported by a fixedly disposed revolvable bearing member 912 so as to be freely rotatable within a vertical plane along a radial direction of the rotation stage 901, is disposed to a peripheral portion of the top surface of the rotation stage 901.
A ring-shaped magnet 920 is disposed to an internal bottom surface of a processing liquid collecting cup 908. The ring-shaped magnet 920 is a permanent magnet which is located below the rotation stage 901, and is formed in a periphery-like configuration which resembles a rotation locus about a rotation axis A of the rotation stage 901. An N-pole is created in a top surface of the ring-shaped magnet 920 while an S-pole is created in a bottom surface of the ring-shaped magnet 920, for example.
The substrate pressing member 911 internally includes a permanent magnet 913. As to the polarities of the permanent magnet 913, an S-pole is created on a pressing surface 911a side and an N-pole is created on one end 911b side. The center of gravity G of the substrate pressing member 911 is located outwardly shifted off a supporting point 912a of the revolvable bearing member 912 (i.e., between the supporting point 912a and the one end 911b). The ring-shaped magnet 920 is moved vertically together with the processing liquid collecting cup 908, toward close to or away from the one end 911b of the substrate pressing member 911.
Prior to and after processing of the substrate W, the processing liquid collecting cup 908 is located at a low position (which is indicated by the dotted line in FIG. 18) while the ring-shaped magnet 920 is away from the one end 911b. Hence, the permanent magnet 913 of the substrate pressing member 911 is rarely subjected to magnetic force of the ring-shaped magnet 920. At this stage, since the center of gravity G is outwardly shifted off the supporting point 912a, the substrate pressing member 911 is in such a posture which releases the substrate W (i.e., the posture shown by the dotted line in FIG. 18).
On the other hand, when the substrate W is processed, the processing liquid collecting cup 908 is moved upward and kept at a position which is indicated by the solid line in FIG. 18. At this stage, the ring-shaped magnet 920 is moved close to the substrate pressing member 911, thereby causing the N-pole of the ring-shaped magnet 920 and the N-pole of the permanent magnet 913 to exert magnetic repulsion to each other. As a result, the substrate pressing member 911 revolves about the supporting point 912a and takes the posture which is shown by the solid line in FIG. 18, whereby the pressing surface 911a is brought into contact with and urged against the outer peripheral portion Wa of the substrate W. Thus, the urging force tightly holds the substrate W between the pressing surface 911a and the side surfaces of the plurality of horizontal position restricting parts 904.
In such a structure as described above, since the ring-shaped magnet 920 is disposed along the rotation locus about the rotation axis A, the substrate W is always subjected to applied urging force while processed. This makes it possible to hold the substrate W while rotating the substrate W throughout the entire period of processing, without idly rotating the substrate W. Further, it is possible to release the substrate W only by moving the processing liquid collecting cup 908 downward.
However, since the conventional substrate holding apparatus 900 described above which is applied to a rotation type substrate processing apparatus requires that the center of gravity G is outwardly shifted off the supporting point 912a, a portion of the substrate pressing member 911 which is outward to the supporting point 912a becomes large and therefore it is difficult to take balance while rotating. This in turn adversely affects the quality of processing of the substrate.
Further, while the substrate holding apparatus 900 described above is applied to a rotation type substrate processing apparatus, such a substrate holding apparatus should allow application to various types of apparatuses which handle substrates (e.g., a substrate transporting apparatus).
In a substrate transporting apparatus, particularly when a substrate having a large diameter is to be handled, it is necessary to transport the substrate as it is inclined at an angle for the purpose of reducing a transportation space. However, in the substrate holding apparatus 900 described above, as the center of gravity G is located outward to the supporting point 912a of the substrate pressing member 911, that is, as the substrate W is released utilizing the gravity force which acts upon the substrate pressing member 911, if the substrate W is inclined at an angle, depending on a positional relationship between the center of gravity G and the supporting point 912a, it may become impossible to release the substrate W any more. Although the gravity force may be replaced with external force such as urging force which is created by a spring in order to release the substrate W which is inclined at an angle, such will make the structure of the substrate pressing part complex.